Plural disk units are mounted on a storage system. Each disk unit is connected to a controller module (CM) via a Serial Attached SCSI (SAS) which is a kind of I/O interface. The storage system is connected to a host computer and writes and reads data in accordance with an I/O command issued by the host computer to the disk unit. That is, the I/O command issued by the host computer to the storage device is controlled by I/O controller firmware (IOCFW) of an I/O controller (IOC) mounted on the CM, and is issued to a corresponding disk unit.
The IOCFW is firmware independent from controller firmware (CFW) which controls the CM. A storage system on which plural redundant CMs are mounted has a mechanism for updating the CFW without stopping a system under operation. This mechanism is called “concurrent firmware loading (CFL).” The CFL employs two systems: a system in which the CFW is updated with turning off and on of the power of the CM; and a system in which the CFW is updated with no operation of the power of the CM (hereafter, referred to as “WarmBoot process”).
FIG. 11 illustrated update of the CFW by the WarmBoot process. In the WarmBoot process, as illustrated in FIG. 11, regarding, for example, CM#0 of a redundancy group 0 and CM#1 of a redundancy group 1, CFW of CM#0 is updated, for example, after CFW of CM#1 is updated. The updated CM#1 and CM#0 are illustrated by shading. That is, the WarmBoot process uses redundancy of the CM, sequentially reboots on the CM basis, and sequentially updates new CFW.
In the WarmBoot process, a high speed process is desired to reduce disconnection of the path with the host computer. For this reason, a download process of the IOCFW which takes second-order time is not included in the WarmBoot process and is performed before the WarmBoot process.
Japanese Laid-open Patent Publication No. 2007-323356, Japanese Laid-open Patent Publication No. 2009-81582 and Japanese Laid-open Patent Publication No. 2003-78946 are examples of the related art.
However, if the download process of the IOCFW and the I/O process to the disk unit are performed in parallel with each other, the I/O process may be undesirably delayed. For example, there is a possibility that, if the download process of the IOCFW and the I/O process to the disk unit are performed in parallel with each other, the I/O process for the I/O command which is being issued to the disk unit is delayed and, as a result, a response to the I/O command is delayed.
The embodiment provides, for example, a storage system capable of reducing delay in an I/O process even if a download process of firmware and an I/O process to storage device are performed in parallel with each other.